Turkeys are one of the animals in that general category that, knowing what we know now, you look at them and you're like "How could smart scientists not look at them and not see that they are obviously a form of dinosaur?"
The idea that birds are descended from dinosaurs is nearly as old as evolution itself, first being proposed by Thomas Huxley in 1868 (Origin of the Species dates from 1859).
The only reason there was a competing evolutionary theory is because it was erroneously thought that birds have a clavicle and dinosaurs don't, so instead it was proposed that birds and dinosaurs have a common ancestor, and that dinosaurs lost the clavicle. Now that they have excavated many more bones paleontologists have since discovered therapod clavicles.
We don't "know" that, because that's not a category of thing we can know or not know. It's a matter of semantics of whether we consider birds dinosaurs, just like it's a matter of semantics of whether we consider people a kind of fish.
"Know" in science is used informally to mean "the preponderance of evidence supports this conclusion. Which could turn out to be wrong if enough contrary evidence is later found."
The scientific consensus today is that the evidence supports the idea that not all the dinosaurs died out when the Chicxulub comet struck 66 million years ago. The ones that could fly or quickly learn how to fly survived and even thrived, and their grandkids are in your back yard right now.
You're not understanding my point. The scientific evidence is that birds are descended from dinosaurs. Scientific evidence can't make birds be dinosaurs, because it's up to us to define "bird" and "dinosaur", and we can define "bird" to exclude dinosaur (and I think most people still do). Just like we can define "fish" and "human", and we can define "fish" to exclude human, even though some fish learned how to walk on land and one of their grandkids is typing this comment right now. Biologists might wish that we all adopt cladistic definitions for types of organisms, but that doesn't the world will follow.
It's almost worse that, if you go back a ways, a lot of the theories were that extinction was fairly incremental--even comet/meteor notwithstanding. So, given essentially total extinction, convergent evolution may not have been a bad theory and may not even have been totally wrong.
The only reason there was a competing evolutionary theory is because it was erroneously thought that birds have a clavicle and dinosaurs don't, so instead it was proposed that birds and dinosaurs have a common ancestor, and that dinosaurs lost the clavicle. Now that they have excavated many more bones paleontologists have since discovered therapod clavicles.